J. England

The effects of age, energy and protein intake on protein turnover and the expression of proteolysis-related genes in the broiler breeder hen.

A study was conducted to determine the changes that occur to proteolysis and related genes due to age, protein, and energy intake in high-yield broiler breeder hens (Gallus gallus). Cobb 700 broiler breeders were randomly assigned to one of six diets in a 2×3 factorial fashion. Two levels of energy (390 and 450 kcal/day) and three levels of protein (22, 24, and 26 g CP/day) were utilized. Protein turnover was determined in the left pectoralis at 22, 26, 31 and 44 weeks. Relative mRNA expression of calpain 2 (CAPN2), proteasome C2 subunit (PSMA1), and F box protein 32 (FBXO32) were determined via RT-PCR at 20, 25, and 44 weeks. Contrasts indicate fractional synthesis rate (FSR) and FBXO32 increase to a maximum at 25-26 weeks and a decrease thereafter. A significant drop in PSMA1 and FBXO32 was observed between 25 and 44 weeks and matched the decrease observed in FBR. No differences were detected in the levels of fractional synthesis and degradation, or the expression of CAPN2, PSMA1, and FBXO32, due to protein or energy intake. In summary, protein turnover was upregulated during the transition into sexual maturity and decreased thereafter. The observed changes in degradation appeared to be mediated by the ubiquitin-proteasome pathway.

Lysine partitioning in broiler breeders is not affected by energy or protein intake when fed at current industry levels

A study was conducted to determine the effects of dietary energy and protein intake on the partitioning of lysine in broiler breeder hens. One hundred twenty-six broiler breeders were randomly assigned to 1 of 6 dietary treatments in a 2 (390, 450 kcal/d) × 3 (22, 24, 26 g of CP/d) fashion. Thirty-six hens were administered a daily oral dose of 15 mg of (15)N-Lys for a period of 2 wk or until first egg. After the 2-wk enrichment period, no isotopes were given for 2 d. After 2 d, a daily oral dose of 15 mg of (2)D4-Lys was administered until the 2nd, 3rd, and 4th egg (saved) after the initial (2)D4-Lys was given, at which point pectoralis muscle was sampled. Weeks 25, 29, and 45 were assessed. Isotopic enrichment of pectoralis muscle, egg yolk, and albumen was determined via gas chromatography-mass spectrometry. The (15)N-Lys was intended to represent endogenous lysine, whereas the (2)D4-Lys was intended to represent dietary lysine. Greater than 78% of all labeled lysine ((15)N and (2)D4-Lys) was found in breast muscle. Endogenous muscle was the main source of lysine for yolk formation at wk 25 and 45. Diet was the main source of lysine for albumen formation at wk 25 and 29. A consistent decrease in the (15)N-Lys in breast muscle from the 2nd to the 3rd egg was observed, while also seeing an increase in the (15)N-Lys in the egg from the 3rd to the 4th egg. No difference in the partitioning of lysine was determined by energy or protein intake at levels typical for the current poultry industry. Rather, age, and possibly rate of production, appear to be the main drivers of lysine partitioning in the broiler breeder hen.

The effects of pullet body weight, dietary nonpyhtate phosphorus intake, and breeder feeding regimen on production performance, chick quality, and bone remodeling in broiler breeders

A 3 × 2 × 2 factorial experiment, consisting of 52 hens per treatment, was conducted to determine the effects of pullet BW, dietary nonphytate phosphorus (NPP), and feeding regimen on performance, progeny quality, and bone remodeling. Cobb 500 broiler breeder pullets were reared to 3 different growth curves: 20% under, Cobb standard, and 20% over. Body weights were recorded weekly and feed adjustments made accordingly. At 21 wk, 624 hens were fed one of 2 breeder diets differing only in the amount of dietary NPP: 0.15 or 0.40%. A normal feeding regimen was appropriate for the particular growth curve; an alternative regimen considered the 3 growth curves together as a flock. At 24, 26, and 29 wk, blood was collected from 5 hens per treatment every 4 h over a 24-h period. Plasma samples were analyzed for total alkaline phosphatase, tartrate-resistant acid phosphatase, parathyroid hormone-related peptide, Ca, and inorganic P. Eggs per hen housed were diminished in hens fed the low dietary NPP and by low pullet target weight. Hens fed low dietary NPP also had lower egg weights but better eggshell quality. Mortality was significantly higher in hens fed low dietary NPP. Breeder tibia relative strength and ash were also significantly lower in hens fed low dietary NPP, regardless of the quantitative amount. Progeny tibia ash was not affected by any treatment. Total alkaline phosphatase responded to pullet BW, however by wk 29, total alkaline phosphatase also became sensitive to dietary NPP. The NPP by pullet BW interaction for tartrate-resistant acid phosphatase levels became significant by 29 wk, and pullet BW was significant at wk 24. The NPP by pullet growth curve interaction was also critical for plasma inorganic P levels throughout the sampling period. In summary, both 0.15% dietary NPP and reared pullets 20% under standard BW negatively affect egg production but do not impair progeny productivity. Body composition appears to be a main contributor in bone remodeling mechanisms, especially during the transition into egg production.

Mechanisms of lipid mobilization towards egg formation in broiler breeder hens using stable isotopes

&NA; The contribution of dietary, mobilized, or newly synthesized fatty acids in yolk formation at different periods of egg production was determined. In an initial experiment, a single dose of 13C‐linoleic acid was administered to pullets at the onset of egg production and their presence in follicles determined over the subsequent 10 days. In a second experiment, pullets were fed a daily 15 mg dose of U‐13C‐glucose beginning 2 wk prior to sexual maturity through the end of the experimental period. A 50 mg meal of U‐13C‐linoleic acid was orally administered approximately 10 d prior to sexual maturity (defined as first egg) representing body linoleic acid. Upon each hens first egg, each bird received a 25 mg meal of 2D31‐linoleic acid representing dietary linoleic acid. All eggs were collected for the next 10 days. The incorporation of labeled linoleic acid and palmitic acid in egg yolk was then determined using GC‐MS. This process was repeated at peak production and at 45 wk of age. At sexual maturity, the deposition of labeled palmitic acid in the yolk was higher compared with its deposition at peak production and 45 wk of age. The deposition of both 13C‐ and 2D31‐linoleic acid increased with hen age. These results suggest that dietary and tissue linoleic acid is utilized to a greater extent in older hens and that lipogenesis (synthesis of palmitic acid) plays a larger role at sexual maturity in the young hen.

Effect of white striping myopathy on breast muscle (Pectoralis major) protein turnover and gene expression in broilers

&NA; A study was conducted to evaluate the effect of white striping (WS) of broiler breast muscle (Pectoralis major) on protein turnover and gene expression of genes related to protein degradation and fatty acid synthesis. A total of 560 day‐old male broiler chicks Cobb 500 were allocated in a total of 16 pens, 35 chicks per pen. A completely randomized design was conducted with a 2 × 3 factorial arrangement (2 scores: severe and normal, and 3 breast meat samples sites). At d 60, 20 birds were randomly selected, euthanized, and scored for white striping. Scoring was either normal (NORM, no WS) or severe (SEV). Also, the same day, 17 birds (16 infused, one control) were randomly selected and infused with a solution of 15 N Phen 40% (APE). Breast muscle tissue was taken for gene expression analysis of the following genes: MuRF1, atrogin‐1, IGF‐1, insulin receptor (IR), fatty acid synthetase, and acetyl CoA carboxylase (ACC). Each bird was humanely euthanized after 10 minutes of infusion and scored for WS (NORM or SEV). Samples of the breast muscle (Pectoralis major) were taken at different layers (3 samples per bird: ventral, medial, dorsal), along with a sample of excreta for 3‐methylhistidine analysis. Out of the 16 breast samples taken, only 10 were selected for analysis based on the WS score (5 NORM and 5 SEV). No significant differences (P > 0.05) were found in fractional synthesis rate (FSR) between SEV WS, NORM and sample sites for breast meat. However, fractional breakdown rate (FBR) was significantly higher in birds with SEV WS compared to NORM (8.2 and 4.28, respectively, P < 0.0001). Birds with SEV WS showed significantly higher (P < 0.05) relative expression of MuRF1 and slightly higher (P = 0.07) relative expression of atrogin‐1 than the NORM birds. These birds also showed lower (P < 0.05) relative expression of IGF‐1 than NORM birds. Further studies are needed to better understand why birds with severe white striping are degrading more muscular protein and mobilizing more fat.

The effect of four different feeding regimens from rearing period to sexual maturity on breast muscle protein turnover in broiler breeder parent stock

&NA; A study was conducted to evaluate the effect of four different feeding regimens on breast muscle protein turnover in broiler breeder Cobb‐500 parent stock (PS) pullets and breeder hens. The four feeding regimens based on BW curves utilized for the study were as follows: Everyday feeding (STD‐ED) (Cobb Standard BW curve), skip‐a‐day feeding (STD‐SKIP) (Cobb Standard BW curve), lighter BW (LBW‐SKIP) (BW curve 20% under), and heavier BW (HBW‐SKIP) (BW curve 20% over). Each feeding regimen was provided to pullets from 4 wk to 21 wk of age. Protein turnover was determined in PS pullets/breeders at 6, 10, 12, 16, 21, 25, 31, 37, 46, and 66 wk of age. A completely randomized design was used with a 4 × 10 factorial arrangement (four feeding regimens, 10 ages), each pullet represented a replicate. Five pullets/breeders at each age were given an intravenous flooding‐dose of 15N‐Phe (15N phenylalanine 150 mM, 40 APE (atom percent excess)) at a dose of 10 mL/kg BW for the determination of fractional synthesis rate (FSR). After 10 min, birds were euthanized and the breast muscle (pectoralis major) excised for protein turnover and gene expression analysis. Excreta was collected from each pullet or breeder for 3‐methylhistidine (3‐MH) analysis. No feeding regimen affected protein turnover. There was an age effect for breast muscle FSR. The FSR in breast muscle of pullets significantly increased from 6 wk to 12 wk and then decreased significantly for 31 wk‐old breeders. FSR in breeder breast muscle increased significantly from 31 wk to 66 wk. There was an age effect for breast muscle fractional breakdown rate (FBR). FBR in breast muscle significantly increased from 21 wk to 25 wk and 31 wk (peak egg production), then significantly decreased at 66 wk. The expression of the genes related to protein degradation (Atrogin‐1, MURF‐1) in breast muscle was significantly higher at peak egg production. Protein turnover in skeletal muscle tissue is believed to be a source of nutrients for egg production.

Stage of egg production regulates protein turnover and lysine partitioning for broiler breeders

Among the regulators of protein turnover, amino acids play a critical role. Lysine, leucine and isoleucine were found to alter protein synthesis, degradation and its regulation (Yoshizawa, 2004; Nakashima et al., 2005; Tesseraud et al., 2008). Furthermore, Tesseraud et al. (2000) reported that differences in the fractional degradation rates (FDR) between fast-growing and slow-growing birds are observed in young birds but not older ones, suggesting a possible age effect.

The effect of sexual maturity and egg production on skeletal muscle (pectoralis major and gastrocnemius) protein turnover in broiler breeder pure lines

Abstract A study was conducted to evaluate the effect of sexual maturity on pectoralis major and gastrocnemius muscle protein turnover in broiler breeder pure lines. Protein turnover in skeletal muscle tissue was determined in 4 broiler breeder pure lines (Line A, Line B, Line C and Line D) at 22, 27, 33, 37, 44, and 50 wk of age. A completely randomized design with a factorial arrangement 4 × 6 (4 lines and 6 time periods (ages)) was used. There were 5 replicates per line/time and each hen represented a replicate. Five hens/line at each age were given an intravenous flooding‐dose of 15N‐phenylalanine (150 mM, 40 atom percent excess (APE) at a dose of 10 mL/kg. After 10 min, birds were euthanized using CO2 asphyxiation and the breast and leg muscle excised and snap frozen in liquid nitrogen for protein turnover analysis. Excreta was collected from each breeder for 3‐methyl histidine (3‐MH) analysis. There was a significant age effect for the breast muscle fractional synthesis rate (FSR), but no main effects (age and line) for leg muscle FSR. The FSR in breast muscle tissue decreased in hens from wk 22 (first egg) to wk 33 (peak egg production). There was a significant age effect on fractional breakdown rate (FBR) in breast and leg muscle. The FBR in breast muscle increased in hens from wk 22 to wk 33 and remained high through wk 37. Breast muscle FBR significantly decreased in hens from wk 37 to wk 50. The FBR in leg muscle tissue increased in hens from wk 33 to wk 37 and then decreased at wk 50. No line effect was seen for FSR or FBR. There is a large increase in skeletal muscle FBR during the transition for the pullet to sexual maturity with increases in skeletal muscle FBR in the breast and leg muscle through peak egg production. Protein turnover in skeletal muscle tissue is believed to be a source of nutrients for egg production.

Evaluation of energy systems in corn and barley based diets and an enzyme complex in broiler chicks

The extensive use of an NE system has not been accepted by the poultry industry because NE feed evaluation is laborious, values have a high variability and the process is expensive. Productive energy (PE), developed by Fraps and Carlyle (1939), was used commercially from 1946-1960 and was unfortunately related to NE. The methodology for the determination of PE is considered the cause for the high variability. De Groote (1968) used one plane of feed intake along with an independent NEm and showed similar variability between ME and NE energy systems. High energy feed costs have caused the poultry industry to dramatically increase the use of exogenous feed enzymes during the past 5 years. The objectives of this study were to compare the ME and NE systems for variability, predicted performance and to determine the extra energy content due to an enzyme complex.

Effect of an enzyme complex and dietary nutrients on endogenous losses of amino acids in chicks

Inconsistencies in expected performance have been noted from feeding exogenous enzymes. Several explanations may exist but it is possible that when feeding diets with exogenous enzymes a metabolic feedback system limits or regulates endogenous digestive enzyme expression, synthesis, and secretion. Labeled amino acids may be an advantage over other methods for measuring endogenous losses because the isotope technique may be used with practical diets. Endogenous amino acid secretions have been shown to be affected by dietary protein, types of fats, and fiber (Siriwan et al., 1989; Danicke et al., 2000) and digestible amino acid requirements should be corrected for the endogenous amino acid losses. The objectives of the present study were to determine endogenous amino acid losses from broilers fed various levels of protein, fat, and fiber with and without added Rovabio MaxTM.